Good Luck!
As you've found, they're pretty rare. The only store I know that used to stock them was Target, and they had a clearance 3/07 or so. Some CPF members stocked up. You might ask in the collector's forums, or post a WTB in Buy Sell Trade. I also create saved searches on eBay for rare items like this - my '7 cell Maglite' gets a hit about once a year :scowl:
Even online places that advertise the rare (non-black, blue, or red) Maglites often don't have them in stock (Alaska Outfitters). Flashlight King has exotic colors listed, but not copper. Same with Quality Items Flashlights, but I don't have experience with them.
You might also have luck searching for "bronze" Maglites - I've seen them called that as welll.
Sorry for the rambling post - HTH